1. Field of the Invention
This invention relates to a magnetic memory, and in particular to a magnetic memory using magnetic bubbles, Bloch line, vertical magnetization or the like as a recording carrier, and to a recording-reproducing method for the magnetic memory.
2. Related Background Art
In a magnetic bubble memory or the like, to detect magnetic bubbles which are a recording carrier, use has heretofore been made of a stretcher which is constructed with a plurality of rows of patterns comprising Permalloy, like patterns for the transfer of magnetic bubbles, being increased successively in the direction of travel of magnetic bubbles, and by the effect of the pattern rows, the magnetic bubbles have been expanded to the same length as the width of the stretcher, and the enlarged magnetic bubbles have been detected by a magnetic resistance effect element or the like, whereby reproduction of information has been accomplished. Also, in a Bloch line memory, the presence or absence of a Bloch line is detected by being converted into the presence or absence of magnetic bubbles and therefore, a detection method similar to that in the above described magnetic bubble memory has been used.
However, in the above-described method, the signal voltage detected is proportional to the number of rows of the stretcher and therefore, the width (the number of rows) of the stretcher rows is detected by being enlarged to 500 to 800 times the diameter of the magnetic bubbles, and the size of the detecting portion for the magnetic bubbles is large, and to obtain a great signal voltage, it has been necessary to form the magnetic resistance effect element, the stretcher, etc. by complicated patterns and thus, a high-degree patterning technique has been required.
Accordingly, when the magnetic bubble memory or the Bloch line memory is to be made into a memory of higher density, it is cumbersome or difficult for the reason set forth above to make it and moreover, the pattern on the magnetic film thus made is very complicated and all circuits and elements for recording, reproduction and transfer cover the entire surface, and this may cause problems such as production of noise, which is turn may lead to a remarkable reduction in detection accuracy.
That is, to effect recording and reproduction at a high speed, there is a limit in the conventional memory structure or recording-reproducing system, and the need for magnetic memories capable of high-speed recording and reproduction is increasing.